HMOs can modulate the small intestinal microbiota and epithelial transcription in a structure-specific manner in pups, with 2'FL activating innate immune pathways and LNnT activating adaptive immune pathways.
Key Findings
Results
Both 2'FL and LNnT enhanced systemic anti-inflammatory capacity without affecting pup growth performance.
C57BL/6J neonatal mice received daily oral gavage of 2'FL or LNnT from postnatal day 7 to day 28
Neither HMO intervention affected standard growth metrics in pups
Both HMOs produced measurable changes in serum inflammatory cytokine profiles consistent with anti-inflammatory effects
The intervention model was designed to simulate early-life HMO exposure analogous to breastfeeding in human infants
Results
2'FL activated innate immune pathways and upregulated genes related to immunomodulation, inflammation, and intestinal barrier function in the small intestine.
Transcriptional profiling of small intestinal epithelium was conducted via multi-omics analysis
2'FL-specific gene expression changes included upregulation of genes associated with innate immune signaling
Genes related to intestinal barrier function were elevated in the 2'FL group
These transcriptional changes were distinct from those observed in the LNnT group, indicating structure-specific effects
Results
LNnT activated adaptive immune pathways and elevated expression of genes involved in immune system development, B-cell and T-cell lineage specification, and immunoregulation in the small intestine.
LNnT-specific transcriptional changes were distinct from those of 2'FL, activating adaptive rather than innate immune pathways
Upregulated genes included those involved in immune system development and differentiation
B-cell and T-cell lineage specification genes were specifically elevated in the LNnT group
This adaptive immune activation profile was identified through epithelial transcriptional profiling of the small intestine
Results
2'FL reduced potentially harmful bacteria such as Streptococcus and enhanced beneficial bacteria such as Ligilactobacillus in the small intestine.
Small intestinal microbiota composition was analyzed as part of the multi-omics approach
Streptococcus, considered a potentially harmful genus, was reduced in the 2'FL group
Ligilactobacillus, considered a beneficial genus, was increased in the 2'FL group
These microbiota shifts were concurrent with elevation of anti-inflammatory metabolites glycoursodeoxycholic acid and sebacic acid
Results
LNnT reduced harmful bacteria such as Desulfovibrio and enhanced beneficial bacteria such as Lachnoclostridium in the small intestine.
Desulfovibrio, associated with harmful effects, was reduced in the LNnT intervention group
Lachnoclostridium, considered beneficial, was increased in the LNnT group
These microbiota changes were concurrent with increased immunomodulatory metabolites tricin and baicalein
The microbiota profile shifts were distinct from those observed in the 2'FL group, reflecting structure-specific HMO effects
Results
Correlation network analysis revealed HMO-specific 'microbiota-metabolite-immune' axes in the small intestine.
Microbial changes were strongly associated with metabolite profiles in both HMO intervention groups
Metabolite profiles in turn correlated with the expression of small intestinal immune-related genes
Metabolite profiles also correlated with serum inflammatory cytokines
The axes were distinct between 2'FL and LNnT groups, reflecting structure-dependent modulation
This tri-directional network analysis linked microbiota, local metabolites, and systemic immune markers
Background
The study established that HMOs exert region-specific effects on the small intestine, a previously poorly characterized aspect of HMO biology.
Prior research on HMOs had focused predominantly on colonic microbiota and host immunity
This study specifically characterized small intestinal microbiota, epithelial transcription, and metabolite profiles
The C57BL/6J neonatal mouse model with gavage from postnatal day 7 to 28 was used to address this gap
Multi-omics analysis encompassed microbiota composition, metabolomics, and epithelial transcriptomics of the small intestine
What This Means
This research suggests that two specific sugars found in human breast milk — called 2'-fucosyllactose (2'FL) and lacto-N-neotetraose (LNnT) — have distinct and beneficial effects on the small intestine during early life. Using newborn mice given these sugars daily for three weeks, the researchers found that both sugars reduced inflammation throughout the body without interfering with normal growth. However, each sugar worked differently: 2'FL appeared to strengthen the gut's first-line defenses (innate immunity) and improve the gut barrier, while LNnT appeared to help develop more specialized immune responses (adaptive immunity) involving immune cells like B-cells and T-cells.
The two sugars also shaped the community of bacteria living in the small intestine in different ways. 2'FL reduced potentially harmful bacteria like Streptococcus and boosted beneficial bacteria like Ligilactobacillus, while also increasing anti-inflammatory molecules in the gut. LNnT reduced harmful bacteria like Desulfovibrio and increased beneficial bacteria like Lachnoclostridium, along with different immune-supporting molecules. These changes in bacteria were linked to changes in gut chemistry, which in turn were linked to changes in immune gene activity and blood markers of inflammation.
This research suggests that the specific structure of a milk sugar matters — different human milk oligosaccharides influence the small intestine's microbial environment, chemical environment, and immune programming in distinct ways. This is significant because most previous research focused on how these sugars affect the large intestine (colon), while this study highlights that the small intestine is also an important target. These findings could inform efforts to develop infant formulas or supplements that more closely mimic the immune-supporting properties of breast milk.
Li Z, Shen Y, Wang W, Xie Z, Huang Q, Zhang B. (2026). Human milk oligosaccharides shape small intestinal microbiota and epithelial transcriptional profile during early life in mice.. Food & function. https://doi.org/10.1039/d6fo00517a